In oil drilling and producing operations, there exists a need for subsea valves they can be actuated from a remote location. Currently, subsea valves are employed that use hydraulic, manual, or electric controls, but these do not work perfectly for a variety of reasons. For example, hydraulic controls, when operated from a position above the water surface, require long hydraulic control lines which may rupture or suffer delays in actuation. Manually operated valves are likewise imperfect for obvious reasons, such as the need for divers or remotely operated vehicles, slow response time, possibly hazardous depths and water conditions, etc. Electric valves that are currently employed in subsea uses are small pilot valves that operate control systems rather than the main flowline. Once the electrically operated pilot valve is triggered, it, in turn, actuates a larger hydraulic valve to control the primary flowline. Since these pilot valves are small, capable of handling only a low fluid volume, and cannot be scaled up to a larger size (as the designs are not linear), they cannot be used in the primary system. Other objections to electric valves, in general, are that: some require continuous power in each valve position and therefore more energy, they may have components that are susceptible to wear which requires more frequent maintenance, they may be too large and complex, or the time response for actuation may be too slow. Consequently, many of these designs are not feasible for subsea applications.
Examples of electromagnetic valves or ones that use windings: Gast et al., U.S. Pat. No. 4,392,632; Lynes et al., U.S. Pat. No. 3,484,074; Kawata et al., U.S. Pat. No. 4,350,319; Hashimoto, U.S. Pat. No. 4,286,767; and Inada et al., U.S. Pat. No. 4,346,736. Magnetically actuated pilot valves are illustrated by: Kah, U.S. Pat. Nos. 4,349,045 and 4,320,023, and Raymond, U.S. Pat. No. 4,053,137.
For these reasons, it is an object of this invention to provide a remotely actuable primary valve for use in the main flowline that is efficient, highly reliable, and preferably simple. It is a further object of this invention to reduce the subsea valve operator size, decrease the response time, and eliminate the need for costly hydraulic umbilicals.